New home for runaway black hole

Galactic ejection may have sent cosmic wanderer through deep space

The most massive black hole ever measured may be an intergalactic hitchhiker that escaped from one galaxy before getting captured by another. If this scenario, laid out in a paper posted February 18 at arXiv.org, is proven correct, it would be the first time astronomers have definitively spotted a black hole that was expelled from its original galactic home.

Computer simulations of galaxy mergers suggest that some supermassive black holes can be nomads: When the galaxies’ central black holes unite, they can emit an enormous surge of energy in one direction. That burst would rocket the newly formed black hole in the opposite direction, the simulations say, often with enough speed to escape the galaxy.

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